The invention relates to a method of providing a plurality of cavities and/or apertures arranged in a pattern in a plate or layer of non-metallic, particularly hard and brittle material.
Plates or layers of this type, which may particularly be made of hard, brittle materials such as glass, (oxidic) or ceramic material, are particularly used in micro-electronic devices such as electro-luminescent gas discharge displays (plasma displays), in field emission displays, cathode ray displays and in displays in which electrons are propagated in ducts having walls of electrically insulating material (referred to as insulating electron duct displays) in which the apertures or cavities are used for manipulating electron currents. They may be formed as (multi-apertured) control plates and provided with (addressable) electrodes cooperating with the apertures, as transport plates having a plurality of parallel cavities (transport ducts), or as apertured spacers (for example, between a control plate and the luminescent screen of a luminescent display).
U.S. Pat. No. 4,388,550 describes a luminescent gas discharge display. This display requires a control plate controlling the individual pixels. This control plate divides the inner space of such displays into two areas, a plasma area and a post-acceleration area. It comprises a "perforated" plate having an array of lines at one side and at the other side an array of columns of metal conductors or electrodes surrounding or extending along the perforations. These enable electrons to be selectively extracted from the plasma area through the apertures to the post-acceleration area and to be incident on the luminescent screen. Other gas discharge displays comprise, for example plates having (facing) cavities.
In a control plate, the number of perforations or apertures in a plate of the type described above is defined by the number of desired pixels.
Present-day television line scan patterns use, for example approximately 500.times.700 pixels having a horizontal pitch of 0.5 mm and a vertical pitch of 0.7 mm. These pixels define the pattern of apertures to be provided in the control plate of electrically insulating material.
It is known from EP 0 562 670 that these patterns can be manufactured by means of an apertured mask and a powder spray process. This process is possible by virtue of the large difference in production rate between the (metallic) mask material and the (non-metallic) material of the object which is to be provided with a pattern of apertures (particularly glass). A problem which appears to occur when using a (metal) mask which is glued onto the plate to be patterned is, however, that the mask is sometimes (locally) detached during spraying, inter alia, with the result that it is no longer seated correctly on the product to be provided with a pattern, which is at the expense of the accuracy of this pattern. Also when the mask is not detached, there is the problem that the apertures made often become larger than is desirable.